PIP supersession

Hello,
I am assisting my brother with a PIP appeal and the hearing is on Monday. I have 2 queries please-I have been my brother's main support with his benefits until recently. I assisted him to complete his forms. He renewed his PIP claim in 2019 and his award was reduced to nil. We went to appeal and in 2020, the DWP changed the decision on the basis of further medical evidence provided by his doctors and the appeal lapsed, he was awarded high rate care and high rate mobility. He received a renewal form in 2022 and his award was reduced to standard care and standard mobility. We put in the MR and the care was put back up to high rate, he remains on the lower rate of mobility and I helped him to submit the appeal as his condition had not improved from 2019 and had in fact, deteriorated.

I would appreciate some advice about the arguments that I can make about the supersession not being based on actual improvement in his needs. The submission has a section confirming the grounds for the supersession and the effective date.
The grounds appear to be that they have not identified a change of circumstances which the claimant should have notified ‘as the evidence didn't suggest there would be an easily identified change the DM decided not to investigate and instead used the report as grounds for supersession’.
‘The previous assessment (2020)awarded 0 points for DL and 0 points for mobility so wasn’t entitled to PIP at either rate. At MR stage the DM agreed with the findings of the assessment and made no changes to the descriptors. At appeal stage the DM empowered their decision and awarded the enhanced rate of DL and enhanced rate of mobility. Whilst I have considered the empowered decision after reviewing the available evidence, I believe it was too generous. The HPA’s medical report...is more up to date and specifically considers limitations related to Mr Mansaray’s ability to complete PIP activities’.

I would like to know if I can challenge this on the basis that they haven’t found actual evidence of an improvement, other than a telephone assessment and as the award would have ended by now, can the Tribunal reinstate the original award or will they need to go through all the descriptors and decide at the hearing? I warned him that he could lose his award but he was adamant that his condition is worse and it is. It has also got worse since the appeal as he suffered another stroke and although this can't be taken into account, can it be considered as information to inform whether supersession was made on insufficient medical evidence?
The second point is the effective date which is the date that the appeal was made in February this year. I don’t understand what they are asking the tribunal to decide when they say-if the tribunal decide an award of PIP is appropriate, their attention is drawn to the fact the effective date of any award is dependent on the regulation used to supersede the awarding decision, and it’s associated considerations. The effective date of any award the Tribunal decide is appropriate, may therefore be different to the effective date of the decision under appeal, as set out at sections 1 and 3 of this appeal response. The Tribunal are respectfully asked to explain how the effective date of the award was arrived at in their decision notice. Can you let me know what I need to prepare for this element, if anything?

Thank you
Ax